JPH09201550A - Decanter type centrifugal separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently wash off impurities adherent to cake since the liquid- removed cake is brought into contact countercurrently with washing liquid while the slanting part of a rotary bowl being agitated forcedly by a screw conveyer. SOLUTION: A partition plate 12 with a modified Z-shaped longitudinal cross section is installed to cross the cross section of a channel on the cake discharge opening 9 side close to the raw liquid distribution opening 10 of a screw conveyer 3. The inner end part of the plate 12 is held by a screw 14 on the peripheral surface of a screw cylinder 4, while the outer end part is loosely held suspendingly to be freely swingable, and a certain gap is left in a rotary bowl 1. When raw liquid slurry is supplied while the bowl 1 being rotated and the screw conveyer 3 being rotated by velocity difference, solid cake is precipitated to the inner wall of the bowl 1 by centrifugal force and transferred to the discharge opening 9 by the conveyer 3. Besides, washing liquid from a supply pipe 6 flows countercurrently to the cake, washes the cake, and is discharged from a separated liquid discharge opening 7 through a separation zone outside the machine. The liquid-removed cake is washed with washing liquid to remove impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decanter type centrifuge having a cake washing mechanism.

[0002]

2. Description of the Related Art A decanter centrifuge introduces an undiluted slurry into a rotating bowl that rotates at a high speed, and a solid content having a large specific gravity (hereinafter referred to as a cake) is settled and separated on an inner wall of the rotating bowl by a centrifugal effect. At the same time, a screw conveyor that rotates at a slightly different speed from the rotating bowl transfers it to the side of the slope (hereinafter referred to as the beach zone), and the beach zone is lifted by the screw conveyor to deliquify the liquid. It is discharged to the outside of the machine from the cake discharge port provided in. As described above, the decanter centrifuge can continuously process the stock solution slurry, continuously discharge the cake, and even if the cake contains fine particles, there is no fear of clogging like a filter. , It is very useful for separating the solid content and the liquid of the stock solution slurry containing fine particles.

[0003]

However, when the undiluted slurry is treated with a decanter type centrifuge and the cake is collected into a product, there are generally the following problems. In the liquid of the stock solution slurry, there are often undesired liquid impurities that remain attached to the product cake, and at this time, when treated with a normal decanter type centrifuge, Adhesion of impurities to the cake cannot be prevented. Therefore, it is desirable to use a decanter centrifuge equipped with a means capable of removing the impurities to an allowable concentration by washing the cake with a washing liquid at the same time as deliquoring, but at present, a satisfactory decanter centrifuge has been developed. Absent.

By the way, the present applicant has previously proposed a decanter for dewatering sludge in Japanese Patent Application No. 5-170863 (Japanese Patent Application Laid-Open No. 7-8).
Patent No. 58). The purpose of the invention of this prior application is to increase the degree of dehydration of the cake, and as a means therefor, as shown in the entire longitudinal sectional view of FIG. 3, a plurality of decanter type centrifugal separators shown in FIG. The press segments 22 are vertically oscillatably provided at appropriate intervals along the screw conveyor 3 in the flow path direction.
That is, in FIG. 3, reference numeral 1 is a rotating bowl including a straight body portion and a beach zone, which is rotated at a high speed by the speed reducer 2. Reference numeral 4 denotes a screw cylinder that is coaxially mounted in the rotary bowl 1. A screw screw conveyor 3 that is inscribed in the inner wall of the rotary bowl 1 is attached to the outer circumference of the screw cylinder. It is rotated with a slight speed difference.

5 is arranged on the axis of the screw cylinder 4,
A stock solution distribution port 1 whose inner end is bored in the screw cylinder 4.
It is a stock solution supply pipe that reaches 0. Reference numeral 7 denotes a plurality of separated liquid discharge ports formed on the same radius of the large-diameter end plate 8 of the straight body portion of the rotating bowl 1. Reference numeral 9 is a cake discharge port for discharging a plurality of dehydrated sludges formed in the circumferential portion of the small diameter end of the beach zone of the rotating bowl.

Reference numeral 22 is a press segment having a sled-shaped vertical section, which is provided between the stock solution distribution port 10 and the cake discharge port 9 of the screw conveyor 3 at appropriate positions across the flow of the concentrated sludge. As shown in the figure, the upstream end of the screw cylinder 4 is attached to the outer peripheral surface of the screw cylinder 4 with screws 14 so that the downstream part can swing. Press segment 2
The vertical cross section of 2 is sled-shaped, and the downstream portion is urged toward the inner wall surface side of the rotating bowl by centrifugal force and squeezed while slidably contacting the flowing sludge to be dehydrated.

As described above, the decanter type centrifuge having the press segment 22 shown in FIG. 4 incorporated therein has a technical object different from that of the present invention. By modifying the shape of the press segment and also modifying the structure of the decanter centrifuge itself shown in FIG. 3, the problems of the conventional decanter centrifuge have been solved.

The present invention has been made based on the above technical background, and when a stock solution slurry containing impurities is subjected to a centrifugal separation process to obtain a sediment-separated deliquored cake as a product, at the same time. An object of the present invention is to provide a decanter-type centrifuge that removes impurities adhering to a deliquored cake by washing it with a washing liquid.

[0009]

In order to achieve such an object, the invention of claim 1 has a screw conveyor that rotates coaxially with the rotating bowl at a slight differential speed, and an end plate of the rotating bowl. In a decanter-type centrifuge including a stock solution supply pipe inserted through an insertion hole, a cleaning solution supply pipe coaxially inserted into the stock solution supply pipe and having a tip extending to a beach zone of the rotating bowl, and the screw. Near the stock solution distribution port of the conveyor, the inner end is swingably attached to the screw barrel across the flow passage cross section on the cake discharge port side of the rotating bowl, and the outer end is slightly smaller than the inner wall of the rotating bowl. A decanter-type centrifuge characterized in that it is provided with partition walls facing each other with a gap.

According to a second aspect of the present invention, in the first aspect, the cleaning liquid is introduced into the beach zone of the rotating bowl from the tip opening of the cleaning liquid supply pipe, and the cake and the cleaning liquid which are scooped up by the screw blades on the beach zone. The decanter centrifuge is characterized in that the cake is washed by contacting the cake in a countercurrent manner.

[0011] The invention of claim 3 is claim 1 or claim 2.
In the decanter centrifuge, the partition plate prevents the separated liquid separated in the separation zone of the rotating bowl from flowing into the beach zone.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall longitudinal sectional view thereof, and FIG.
FIG. 6 is an enlarged perspective view showing a partition plate which is a II part. First, FIG.
In, the structures of the rotating bowl and the screw conveyor will be described. The same reference numerals as those in FIGS. 3 and 4 denote substantially the same members as those in FIG. In the figure, reference numeral 1 denotes a rotating bowl composed of a straight body portion (separation zone) and a beach zone, which is rotated at a high speed by a reduction gear 2. A screw cylinder 4 is mounted in the rotary bowl 1, and a spiral screw conveyor 3 that is inscribed in the inner wall of the rotary bowl 1 is attached to the outer circumference of the screw cylinder. These are rotated by the speed reducer 2 at a slightly different speed from the rotating bowl 1.

[0013] 5 is disposed on the axis of the screw cylinder 4,
It is a supply pipe for supplying a stock solution slurry, the inner end of which reaches the stock solution distribution port 10 formed in the middle of the screw cylinder 4. Reference numeral 6 denotes a cleaning liquid supply pipe coaxially inserted into the undiluted liquid supply pipe 5 and having a tip extending near the minimum diameter portion of the beach zone. Reference numeral 7 denotes a plurality of separated liquid discharge ports formed on the same radius of the large-diameter end plate 8 of the straight body portion of the rotating bowl 1. Reference numeral 9 is a cake discharge port for discharging a plurality of cleaning cakes formed in the circumferential portion of the small diameter end of the beach zone of the rotating bowl.
A plurality of cleaning liquid distribution ports 11 are formed in the beach zone of the screw cylinder 4. Reference numeral 13 is an insertion hole provided in the end plate 8 for inserting the stock solution supply pipe 5.

Next, the partition plate 12 shown in FIG. 2 will be described. 12 is a stock solution distribution port 1 of the screw conveyor 3
It is a partition plate having a modified Z-shaped vertical cross section, which is provided at an appropriate position across the flow path cross section on the cake discharge port 9 side near 0, and has a screw on the outer peripheral surface of the screw cylinder 4 at its inner end. 14
Thus, the outer end is supported so as to be loosely suspended so as to be swingable, and the bent portion of the outer end faces the inner wall surface of the rotating bowl 1 with a slight radial gap δ. doing.

In such a structure, while the rotary bowl 1 is rotating at a speed of 4000 to 5000 rpm and the screw conveyor 3 is rotating in the same direction with a speed difference of 10 to 20 rpm, the stock solution supply pipe 5 The undiluted solution slurry supplied into the screw cylinder 4 is introduced into the rotating bowl through the undiluted solution distributing port 10, and the solid cake is settled on the inner wall of the rotating bowl 1 by the action of centrifugal force.
The screw conveyor 3 moves to the cake outlet 9 along the beach zone. On the other hand, the cleaning liquid supplied by the cleaning liquid supply pipe 6 is introduced into the smallest diameter part of the beach zone and flows countercurrently with the cake toward the separation zone of the rotating drum along the beach zone to efficiently clean the cake. After that, it is discharged from the separation liquid discharge port 7 to the outside of the machine through the separation zone.

During this time, the stock solution distribution port 10 is fed to the rotating bowl 1
The separated liquid introduced into the inside and separated from the solid content moves toward the separated liquid discharge port 7 along the spiral flow path formed by the screw conveyor 3. At this time, the partition plate 12
Prevents the separation liquid from moving to the beach zone side and mixing with the cleaning liquid. Then, the solid cake can smoothly pass through the clearance δ between the outer end of the partition plate 12 and the inner wall of the rotating bowl 1 without being hindered from moving.

From the above description, it can be seen that the present invention is greatly different from the structure of the decanter type centrifugal separator shown in FIGS. 3 and 4 in the following two points. (1) In the present invention, there is the cleaning liquid supply pipe 6 which reaches the vicinity of the cake discharge port 9 of the rotary bowl 1 and is coaxially inserted into the stock liquid supply pipe to supply the cleaning liquid to the beach zone. On the other hand, in the decanter type centrifuge of FIG. 3,
No cleaning liquid supply pipe is provided. (2) The partition plate 12 according to the present invention has a modified Z-shaped vertical section, which prevents the separated liquid from flowing into the beach zone and has a function of not hindering the movement of the cake. The press segment 22 of FIG. 4 has a sled-shaped cross section and has a function of pressing and dehydrating sludge.

In the above embodiment, the cleaning liquid is supplied near the cake outlet of the beach zone, but in order to reduce the liquid content of the cleaning cake, the cleaning liquid may be supplied to the middle portion of the beach zone. It is possible. Further, it is possible to divide the beach zone into multi-stage washing zones by providing a plurality of partition plates and correspondingly distributing the washing liquid.

[0019]

According to the present invention having the above-mentioned structure and action, the following effects can be obtained. (1) The cake that has been settled and separated in the straight body of the rotating bowl is
Since the inclined portion of the rotating bowl is forcibly stirred by the screw conveyor and comes into contact with the cleaning liquid countercurrently, the cake-adhering impurities are cleaned and removed very efficiently. (2) The sedimentation and separation of the cake and the washing with the washing liquid can be performed with only one centrifuge, so that the equipment cost and the equipment installation area can be reduced.

[Brief description of drawings]

FIG. 1 is an overall vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a partition plate which is a II part of FIG.

FIG. 3 is an overall vertical cross-sectional view showing a sludge dewatering decanter, which is a prior application of the present applicant.

4 is a perspective view showing the press segment 22 of FIG. 3. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1; Rotating bowl, 2; Reducer, 3; Screw conveyor, 4; Screw barrel, 5; Stock solution supply pipe, 6; Cleaning solution supply pipe, 7; Separation solution discharge port, 8; End plate, 9; Cake discharge port, 10; stock solution distribution port, 11; cleaning solution distribution port, 12; partition plate, 13; intubation hole, 14; screw, 22; press segment.

Claims (3)

[Claims] 1. A decanter-type centrifuge comprising a screw conveyor that rotates coaxially with a rotating bowl at a slight differential speed, and a stock solution supply pipe inserted through an insertion hole of an end plate of the rotary bowl. A cleaning liquid supply pipe coaxially inserted into the supply pipe and having a tip extending to the beach zone of the rotating bowl, and a flow passage cross section on the cake discharge port side of the rotating bowl near the raw liquid distribution port of the screw conveyor. A decanter-type centrifuge having an inner end swingably attached to a screw cylinder and an outer end having a partition plate opposed to the inner wall of the rotary bowl with a slight clearance. Separator. 2. The cleaning liquid according to claim 1, wherein the cleaning liquid is introduced into the beach zone of the rotating bowl from the opening of the tip of the cleaning liquid supply pipe,
A decanter-type centrifuge characterized in that the cake to be scooped up by a screw blade and the cleaning solution are brought into countercurrent contact with each other on the beach zone to wash the cake. 3. The decanter type centrifugal separator according to claim 1 or 2, wherein the partition plate prevents the separated liquid separated in the separation zone of the rotating bowl from flowing into the beach zone.